My BLOG about my journey into the invisible world of ultraviolet UV photography, simulated bee, butterfly and animal vision photography and the special lenses, filters and lighting needed to make it work - also in HD video + 3D stereo.

Tuesday, May 31, 2011

Just preparing and testing for a field trip, so some output here for your - hopefully - viewing pleasure...

UV camera, Baader-U filter, my ReflectionDisc for in-camera whitebalancind, leading to the following UV "color" palette:

[click on image to see a larger one]

The 375-390nm group (violet UV reflection):

The 350-370nm group (yellow UV reflection):

That last shot, a Helianthus tuberosus (in female state) image is quite interesting, as the full blooming flower shows a 350-370nm reflection, whereas the younger buds show some in the 375-390nm range. Obviously there are development stages in UV reflections, I would assume .

[excuse the little motion blur in some images, it was quite windy today...]

Wednesday, May 25, 2011

To figure out the approximate spectral response of my full spectrum converted camera, I played around a bit with some gratings and my stabilized, continuous Xenon light source. I also found a linear spectra of my Xenon lamp, so with its help an approximate calibration of the recorded spectra is possible.

The first line is the Xenon spectra, the second the unfiltered spectra as recorded by the UV sensitive camera, the third line filtered through a Didymium calibration filter.

[click on image to see a larger one]

So from that and the color tests I published before, I would estimate that this full spectrum camera has a 320nm - 1000nm UV-VIS-NIR response. Actually I think it is more, as in such an image the exposure range limits the recording of fainter responses at the ends of the spectrum.

Found some better software which allows to read out such optical spectra. Here the results of using such:

On top the spectra as taken by photo, underneath the read out and calibrated spectra using known data high pressure Xenon spectra. The x-axis is in Angstroms, so knowing that 10A equals 1nm, it is easy to understand.

Again, please remember that the grating used was not really made for UV, but for VIS + NIR, so no wonder the spectra ends around 380nm. The real sensitivity to UV of that converted camera is quite higher, but I haven't found its limits yet.

As I was taking some measurements with the Coastal Optics UV-VIS-NIR Apo 60mm, I thought why not also testing a few other fully color-corrected lenses while I'm at it... (forgot the Coastal Optics 105mm, unfortunately...)

[click on image to see a larger one]

[validity: approx 310 - 750nm]
Interesting to note, how similar the older designs (Zeiss UV-Sonnar 105mm and LOMO UFAR-12 41mm) are, but the Pentax Ultra Achromatic Takumar 85mm has a notch in terms of transmission. Then comes the UV-Nikkor 105mm and the newer CERCO 94mm; the newest and best being the most advanced development, the Coastal Optics UV-VIS-NIR Apo 60mm.

Saturday, May 21, 2011

Well, I had presented my Reflection Disc solution, which had been tested against (R) Spectralon when a forum member came up with the remark, that there are commercially available gray cards available, claiming to also work equally well in UV. So of course I got one and run tests against the industry standard (R) Spectralon as well as against my Reflection Disc (approx 75% reflection). That WhiBal Card has a white, a black area also, as well as a large gray area - all have been measured.

The ReflectionDisc certainly is not perfect, but works quite well in practice and delivers jpgs directly out of the camera with acceptable whitebalance for UV, VIS and NIR, also for a quick exposure check.

Here the photographic proof of the above - reflected UV using Baader-U filter and Xenon flash.

The card should be "white" or light gray, which it isn't. The cubes are Spectralon laying on my ReflectivityDisc.

It does work well in NIR though - here the card appears gray as it should be.

Gasometer Oberhausen, Germany 11. March 2016 - 30 December 2017 "Wonders of Nature" exhibit with large size prints of Zinnia flowers in human vision, UV and simulated bee vision, as well as a video presentation of various flowers in VIS + UV showing hidden nectar guides. 1.5 million visitors have seen this exhibit.

Carl Bosch Museum, Heidelberg Germany 12. September 2015 - 3. April 2016 exhibit about colors and dyes with a video animation with some of my best works in human vision, simulated bee and butterfly vision

About Me

This is my blog about my film and photographic work in 3D, ultraviolet UV, infrared IR and fluorescence using special lenses and equipment. All text and images carry my copyright and I do not allow to link to or copy / download from my site or any parts thereof without my prior permission.
email me in case of questions or interest in my images (esp. for non-profit orgs) or if you need a complete camera + lens + filter + light set for UV photography:
postmaster AT macrolenses.de